[1] Univ Paris 06, Ecole Normale Super, Lab Phys Stat, CNRS UMR8550, Paris, France
[2] Univ Paris 06, Ecole Normale Super, Dept Biol, CNRS UMR8550, Paris, France
[3] Univ Paris 07, Ecole Normale Super, Dept Biol, CNRS UMR8550, Paris, France
[4] Ecole Normale Super, Dept Chim, Lab Pasteur, F-75231 Paris, France
[5] Univ Paris 07, Ecole Normale Super, Lab Phys Stat, CNRS UMR8550, Paris, France